1. Field of the Invention
The present invention relates to an image forming apparatus for utilizing an electrophotographic process, and in particular to an image forming apparatus, such as a copying machine or a printer, that transfers a toner image borne on an image bearing member to an intermediate transfer member unit, and then transfers the toner image from the transfer member to a transfer material.
2. Related Background Art
An image forming apparatus is well known that performs the first transfer, to an intermediate transfer member unit, of a toner image that is formed on an electrophotographic photosensitive drum (hereinafter referred to as merely "photosensitive drum"), which serves as an image bearing member, and the second transfer of the toner image borne on the intermediate transfer member unit to a transfer material. Such an apparatus is effective as a color image forming apparatus or as multi-color image forming apparatus that sequentially transfers and laminates images including a plurality of color components, such as color image data and multi-color image data, and outputs the resultant color or multi-color image. It also is effective as an image forming apparatus that includes a color image forming function and a multi-color image forming function. With these apparatuses, an image that has no aberration in lamination of images for individual color elements (color aberration) can be acquired.
A well known intermediate transfer member unit and a photosensitive drum, which are durable parts, are designed to be detachable from the main body of the apparatus in a direction parallel to their rotary shafts in order to facilitate the exchange.
An intermediate transfer member unit that is detachable from the main body of an apparatus in a direction perpendicular to its rotary shaft has been proposed in Japanese Patent Laid-Open Application No. 9-6087. If the intermediate transfer member unit can be detached from the main body of the apparatus in the direction parallel to the rotary shaft, an opening that is large enough to permit the intermediate transfer member unit to pass through must be formed in the frame of the apparatus that supports the rotary shaft of the transfer member. As a result, the strength of the apparatus is reduced and the rotation of the intermediate transfer member unit will be uneven due to the reduction in the strength of the apparatus. The intermediate transfer member unit proposed in the above conventional art eliminates this problem. In the above above conventional art, other durable parts, such as a photosensitive drum, are not desired as being detachable from the main body of the apparatus for exchange.
As in the conventional, well known image forming apparatus, when the intermediate transfer member unit and the photosensitive drum are detachable from the apparatus, an opening large enough for both the intermediate transfer member unit and the photosensitive drum to pass through is required in an apparatus frame that supports the rotary shafts of the intermediate transfer member unit and the photosensitive drum. As a result, the strength of the apparatus is reduced and the rotation of the intermediate transfer member unit and the photosensitive drum will be uneven due to the reduction of the strength.
In addition, when, for example, a plurality of durable parts, such as an intermediate transfer member unit and a photosensitive drum, are detachable from the apparatus in a variety of directions, i.e., either from the front, from the rear, from the top, from the left or from the right, a user will become confused as to what durable part is to be exchanged in which direction.